In the final surfing scene, Mack's hair goes from up, to down, to up again while in the water surfing.
When the Bikers enter the shindig at Big Momma's the Surfers can be seen across the room, but when they begin walking further inside the surfers are by the doors in which they entered.
In the last moment of the number "Surf Crazy", Tanner does a somersault onto his surfboard, landing with his bottom half not on the surfboard. The camera flashes to Mack, then back to Tanner, where his body is fully on the surfboard.
When we first see the bikers Lugnut is wearing his Red converse with white socks, but when they start to dance to "Crusin for a Brusin" he is wearing black socks and his trousers are rolled up.
After "Surf Crazy", all of the surfers run into Big Momma's. Brady and Mack are in the middle of the group going into the restaurant, but are the last to enter the door when the camera pans to the inside.
In some 1962 scenes there are a 1965 Ford F-Series pickup and a 1965 Ford Thunderbird.
In "Make it Stop," you can see the modern parts of Puerto Rico in the background.
In the scene that the weather machine is about to blow out and the surfers and bikers all are running away, the blonde surfer girl with blue clothes can be seen leaving, but a second after she's back next to the machine and starts to run again.
In 'Can't Stop Singing' when Brady says, "Don't make it stop!" his mouth doesn't form the words.
At the end of the 'Surf's Up' dance, Brady picks Mack up, and we hear him say "All right!", but his mouth doesn't move.
Mack says multiple times that the musical surfers go in the water and their hair never gets wet, yet when they first arrive in the musical world, all the females in the water clearly have wet hair.
(at around 1 hour 28 minutes) When they start dancing again, Mack starts to do one move, then very quickly changes to another, showing that she did the wrong move. This happens so quickly, it's a "blink and you'll miss it" moment, which is probably why the editors decided to leave it.